Visible light chromophore excitation for microorganism control

Abstract

Visible light disinfection is a healthcare technology wherein violet light is used to inactivate pathogens such as bacteria, fungi, and viruses. The present invention overcomes the limitations of continuous irradiance in whole-room environments by pulse width modulation of the light sources and increasing the instantaneous irradiance while maintaining average irradiance and hence light power requirements. The invention further discloses the use of multispectral light sources wherein the pulse modulation frequencies are synchronized and the phase of the spectral components are offset in order to maximize synergistic or antagonistic responses to intracellular chromophore excitation.

I claim: 
     
       1. A method for exciting two different chromophores in a microorganism, the method comprising:
 illuminating the microorganism with first light having a first pulse frequency and a first wavelength between 380 nm and 750 nm; while 
 illuminating the microorganism with second light having a second pulse frequency and a second wavelength between 380 nm and 750 nm; 
 wherein the second wavelength is different to the first wavelength; 
 wherein the first and second pulse frequencies are different; 
 wherein the first and second pulse frequencies are integral multiples of a fundamental frequency; and 
 wherein a pulse train of the first light has a zero, positive or negative phase difference with respect to a corresponding pulse train of the second light. 
 
     
     
       2. The method of  claim 1 , wherein the microorganism is in air, in water, in a horticultural growth medium, on mammalian skin, on a plant root or on a plant shoot system. 
     
     
       3. The method of  claim 1 , comprising providing further illumination, which, in combination with the first light and the second light, provides white light for general illumination with a predetermined correlated color temperature and predetermined color rendering properties. 
     
     
       4. The method of  claim 3 , wherein the further illumination has a pulse frequency of 2-500 times greater than the fundamental frequency. 
     
     
       5. The method of  claim 1 , comprising providing further illumination, which, in combination with the first light and the second light, provides light corresponding to a circadian cycle, circannual cycle or life cycle of a plant. 
     
     
       6. The method of  claim 1 , wherein each of the first and second wavelengths is tuned to an absorption peak of the corresponding chromophore. 
     
     
       7. The method of  claim 1 , wherein:
 the first light and the second light are monochromatic; and 
 a radiant flux that is incident upon the microorganism from the first light and the second light combined is less than a radiant flux that would be required to achieve said excitation of the chromophores using quasimonochromatic or broadband light that encompasses the first and second wavelengths. 
 
     
     
       8. The method of  claim 1 , wherein the phase difference is non-zero. 
     
     
       9. The method of  claim 1 , further comprising:
 detecting, with a sensor, a parameter of an environment of the microorganism; and 
 in response, adjusting either or both of a peak radiant flux and a duty factor, of either or both of the first light and the second light. 
 
     
     
       10. The method of  claim 1 , wherein each chromophore is a flavin or a porphyrin. 
     
     
       11. A luminaire comprising:
 a first light emitting element (LEE) that emits first light at a first pulse frequency with a first wavelength between 380 nm and 750 nm; and 
 a second LEE that emits second light at a second pulse frequency with a second wavelength between 380 nm and 750 nm; 
 wherein the second wavelength is different to the first wavelength; 
 wherein the first and second pulse frequencies are different; 
 wherein the first and second pulse frequencies are integral multiples of a fundamental frequency; and 
 wherein a pulse train of the first light has a controllable phase difference with respect to a corresponding pulse train of the second light. 
 
     
     
       12. The luminaire of  claim 11 , wherein the first light and the second light are monochromatic. 
     
     
       13. The luminaire of  claim 12 , wherein the first wavelength is between 400-410 nm and the second wavelength is between 520-530 nm. 
     
     
       14. The luminaire of  claim 11  further comprising one or more further LEEs that generate optical radiation with one or more wavelengths in a range of 200 nm to 3000 nm, wherein the optical radiation is monochromatic, polychromatic, multispectral or quasimonochromatic. 
     
     
       15. The luminaire of  claim 14 , wherein the optical radiation corresponds to a circadian cycle, a circannual cycle or a life cycle of a plant. 
     
     
       16. The luminaire of  claim 11  further comprising one or more further LEEs that generate optical radiation with one or more wavelengths in a range of 380 nm to 750 nm. 
     
     
       17. The luminaire of  claim 16 , wherein the optical radiation is emitted at a pulse frequency 2-500 times greater than the fundamental frequency. 
     
     
       18. The luminaire of  claim 11 , wherein a ratio between the first and second pulse frequencies is non-integral. 
     
     
       19. A system for exciting two different chromophores in a microorganism, the system comprising:
 a luminaire having:
 a first light emitting element (LEE) that emits first light at a first pulse frequency with a first wavelength between 380 nm and 750 nm; and 
 a second LEE that emits second light at a second pulse frequency with a second wavelength between 380 nm and 750 nm; 
 wherein the second wavelength is different to the first wavelength; 
 wherein the first and second pulse frequencies are different; 
 wherein the first and second pulse frequencies are integral multiples of a fundamental frequency; and 
 wherein a pulse train of the first light has a controllable phase difference with respect to a corresponding pulse train of the second light; 
 
 a driver coupled to drive each LEE with an independently variable duty factor and an independently variable peak radiant flux output and to control the phase difference; 
 a sensor configured to detect a parameter of an environment of the microorganism; and 
 a controller configured to adjust, based on the parameter, either or both of a peak radiant flux and a duty factor, in either or both of the first light and the second light. 
 
     
     
       20. The method of  claim 1 , comprising controlling the phase difference.